March 28, 2026 David Lacoursière

Peterbilt 579 Headlight Replacement: Sizes, Types, and Step-by-Step Installation

Replacing headlights on a Peterbilt 579 is one of the most common maintenance jobs for this popular Class 8 tractor. Whether your headlights have hazed over from years of UV exposure, taken damage from road debris, or developed moisture intrusion from failed seals, a fresh set of headlight assemblies transforms both the appearance and night driving safety of your 579.

This guide walks through the Peterbilt 579 headlight replacement process, covers the different headlight options available, and helps you choose the right assemblies for your truck and budget.

Peterbilt 579 Headlight Types and Model Year Differences

The Peterbilt 579 has been in production since 2012, and the headlight design has evolved across several major revisions. The key distinction is between the original 579 (2012-2021) and the refreshed Model 579 (2022+), which received updated front-end styling including new headlight housings.

2012-2021 models: These use a composite halogen headlight assembly with a rectangular shape and integrated turn signal. The headlight mounts to the front header panel with three or four bolts and a single electrical connector.

2022+ models: The refreshed 579 uses a restyled headlight with a more angular design. These housings are not interchangeable with the earlier models, so always verify your model year before ordering.

We carry multiple Peterbilt 579 headlight options including the Peterbilt 579/587 headlight assembly, the 2022+ Peterbilt 579 headlight assembly, and the standard Peterbilt 579 headlight — all built to match OEM mounting points and specifications.

Signs Your 579 Headlights Need Replacement

Not every headlight issue requires full assembly replacement. Here’s how to determine whether you need new bulbs, restoration, or complete replacement:

Cloudy or yellowed lenses: UV exposure breaks down the polycarbonate lens coating over time. Mild hazing can be addressed with headlight restoration kits, but severe yellowing or internal hazing (moisture between the lens and reflector) means replacement is the only fix.

Moisture inside the housing: Condensation inside the headlight indicates a failed seal. Small amounts of moisture may clear on their own, but persistent fogging or visible water pooling inside the housing calls for replacement — trapped moisture corrodes the reflector and electrical contacts.

Cracked or broken lens: Any physical crack in the headlight lens is an immediate replacement situation. Cracks allow water, dirt, and debris into the housing and rapidly destroy the internal components. Driving with cracked headlights also violates DOT regulations.

Dim output despite new bulbs: If you’ve replaced the bulbs but the headlights are still noticeably dim, the reflector inside the housing has likely degraded. The metallic reflector coating breaks down with heat and age, reducing the amount of light directed forward. New assemblies are the only solution.

How to Replace Peterbilt 579 Headlights

Headlight replacement on the 579 is a straightforward job that most mechanics can complete in 30-45 minutes per side. Here’s the process:

Step 1: Disconnect the battery. Always disconnect the negative battery terminal before working on the electrical system. This prevents short circuits and protects sensitive electronic components.

Step 2: Remove the mounting bolts. The headlight assembly is held in place by three bolts (some model years use four) accessible from the top and side of the housing. Use a 10mm socket and be careful not to drop the bolts behind the bumper.

Step 3: Disconnect the electrical connector. The main wiring harness connector is located at the back of the headlight assembly. Press the release tab and pull the connector straight back — don’t twist or pull at an angle, as this can damage the pins.

Step 4: Remove the old headlight. Slide the assembly forward and out of the mounting area. There may be alignment pins or tabs that need to clear the surrounding body panels.

Step 5: Install the new assembly. Reverse the removal process. Slide the new headlight into position, connect the electrical connector, and install the mounting bolts. Tighten bolts evenly and avoid overtightening — the housing ears can crack if forced.

Step 6: Aim the headlights. After installation, headlight aim needs to be checked and adjusted. Park the truck on level ground 25 feet from a wall and verify that the beam pattern is level and centered. The 579’s headlight adjusters are accessible from behind the housing.

LED vs. Halogen Headlights for the Peterbilt 579

The stock 579 comes with halogen bulbs, but LED upgrades are increasingly popular. Here’s the tradeoff:

Halogen advantages: Lower upfront cost ($200-400 per assembly), simple plug-and-play replacement, no compatibility concerns with the truck’s electrical system, and proven DOT compliance.

LED advantages: 2-3x brighter output, 50,000+ hour lifespan vs. 1,000-2,000 hours for halogen, lower electrical draw (reduces alternator and battery load), and instant-on brightness with no warm-up time.

For fleets, the total cost of ownership calculation usually favors LED — one LED headlight lasts the equivalent of 25+ halogen bulb replacements. For a comprehensive comparison across all truck brands, read our LED vs halogen vs projector headlight comparison.

Peterbilt 579 Headlight Specifications

Low beam bulb: H11 (halogen models) — 12V/55W

High beam bulb: 9005/HB3 — 12V/65W

Turn signal: 3157A (amber)

Marker light: 194/168 (some models)

When buying replacement bulbs, stick with name-brand options from Sylvania, Philips, or GE. The bargain-brand bulbs are rarely worth the savings — they burn out faster and produce less consistent light output. If you’re upgrading to LED bulbs within existing housings, make sure the LED bulbs are designed for the specific socket type and include proper heat sinks.

Common Mistakes to Avoid

Touching halogen bulbs with bare hands: Skin oils on halogen bulbs create hot spots that cause premature failure. Always handle bulbs with clean gloves or a paper towel.

Ignoring headlight aim after replacement: New headlights out of the box are not aimed for your specific truck. Driving with misaimed headlights blinds oncoming traffic and reduces your own visibility.

Replacing only one side: If one headlight has degraded, the other is usually close behind. Replacing both sides at once ensures matched light output and appearance. It’s also more efficient — you’re already set up with the tools and your truck is already in the shop.

Buying based on price alone: The cheapest headlight assembly often uses thin lens material that hazes quickly, poor-quality reflectors, and weak seals. A slightly higher-quality aftermarket assembly from a reputable supplier will outlast the cheapest option by years.

Related Truck Parts Guides

Previous article Hino Box Truck Parts and Maintenance Guide: 155, 195, 238, 258, 268, 338, and 358 Models

Next article Freightliner Cascadia Parts: Complete Replacement Guide for Every Component